My Chess Books Vol - 11: Secrets of Opening Surprises (Vol2) by Jeroen Bosch ed.
At $11.00 used this book was a 50% discount. The analysis presented in it is strong but not an overload as it is the case with many other books of this kind. This book is part of a multi volume series that focuses on rare openings and uncommon variations in the mainline ideas for Benonin, French etc. I have not used this book much yet as I find that I am not strong enough a layer to pull of some of the ideas presented...that being said it is a great study aid for those days when you feel like chess theory is what you want to engage in.